William Allen Zajc

Profile

My research interests center on the experimental study of quantum chromodynamics (QCD). Far and away the most exciting topic in nonperturbative QCD is the role of QCD in determining the properties of bulk hadronic matter. The excitement results from theoretical predictions that highly compressed nuclear matter will undergo a phase transition, where the quarks and gluons are no longer confined to individual nucleons. The formation and experimental detection of such a state (called the quark-gluon plasma or QGP) is the outstanding question in high-energy nuclear physics.

Previously, our group investigated these issues in fixed-target heavy-ion collisions at the Brookhaven AGS. In particular, we concentrated on the implementation of a fast Level II trigger for a magnetic spectrometer, which allowed us to select events of maximum physics interest, such as those events containing strange particles (kaons) and/or those with two-like bosons (pions or kaons). Such data were used to study f meson production and to determine the size and lifetime of the production region using two-boson interferometry.

Currently I am spokesperson for the PHENIX experiment at BNL's Relativistic Heavy-Ion Collider (RHIC). This machine provides colliding beams of Au nuclei at 100 A GeV, thereby extending the study of nuclear collisions into a truly fundamental regime. RHIC began operations in 2000, and the first results (for examples, see my publications below) both verify our expectations and also challenge out understanding of dense hadronic matter. Many exciting investigations will be undertaken by PHENIX in the next decade to resolve the issues raised by the first RHIC data. It is already clear that PHENIX has achieved its goal to study both the perturbative and non-perturbative regime at RHIC in one apparatus. As an added benefit, PHENIX has also begun studies of the spin structure of the nucleon using RHIC's unique ability to collide polarized protons. Over the past decade, our group at Columbia has played a major role in the design, construction, and management of PHENIX, and now it is particularly gratifying to see the robust design of this device in action.

I've tried to select a representative set of papers from my entire research career. The selection criteria are somewhat arbitrary; for a nearly complete listing of my publications click here.